Add SIMD optimization for `bytes.hex()`, `bytearray.hex()`, and `binascii.hexlify()` as well as `hashlib` `.hexdigest()` methods using platform-agnostic GCC/Clang vector extensions that compile to native SIMD instructions on our [PEP-11 Tier 1 Linux and macOS](https://peps.python.org/pep-0011/#tier-1) platforms.
- 1.1-3x faster for common small data (16-64 bytes, covering md5 through sha512 digest sizes)
- Up to 11x faster for large data (1KB+)
- Retains the existing scalar code for short inputs (<16 bytes) or platforms lacking SIMD instructions, no observable performance regressions there.
## Supported platforms:
- x86-64: the compiler generates SSE2 - always available, no flags or CPU feature checks needed
- ARM64: NEON is always available, always available, no flags or CPU feature checks needed
- ARM32: Requires NEON support and that appropriate compiler flags enable that (e.g., `-march=native` on a Raspberry Pi 3+) - while we _could_ use runtime detection to allow neon when compiled without a recent enough `-march=` flag (`cortex-a53` and later IIRC), there are diminishing returns in doing so. Anyone using 32-bit ARM in a situation where performance matters will already be compiling with such flags. (as opposed to 32-bit Raspbian compilation that defaults to aiming primarily for compatibility with rpi1&0 armv6 arch=armhf which lacks neon)
- Windows/MSVC: Not supported. MSVC lacks `__builtin_shufflevector`, so the existing scalar path is used. Leaving it as an opportunity for the future for someone to figure out how to express the intent to that compiler.
This is compile time detection of features that are always available on the target architectures. No need for runtime feature inspection.
Remove private _PyUnicode_TransformDecimalAndSpaceToASCII() and other
private _PyUnicode C API functions: move them to the internal C API
(pycore_unicodeobject.h). No longer most of these functions.
Replace _testcapi.unicode_transformdecimalandspacetoascii() with
_testinternal._PyUnicode_TransformDecimalAndSpaceToASCII().
Py_REFCNT(), Py_TYPE(), Py_SIZE() and Py_IS_TYPE() functions argument
type is now "PyObject*", rather than "const PyObject*".
* Replace also "const PyObject*" with "PyObject*" in functions:
* _Py_strhex_impl()
* _Py_strhex_with_sep()
* _Py_strhex_bytes_with_sep()
* Remove _PyObject_CAST_CONST() and _PyVarObject_CAST_CONST() macros.
* Py_IS_TYPE() can now use Py_TYPE() in its implementation.
Move Include/pystrhex.h to Include/internal/pycore_strhex.h.
The header file only contains private functions.
The following C extensions are now built with Py_BUILD_CORE_MODULE
macro defined to get access to the internal C API:
* _blake2
* _hashopenssl
* _md5
* _sha1
* _sha3
* _ssl
* binascii
Avoid a temporary buffer to create a bytes string: use
PyBytes_FromStringAndSize() to directly allocate a bytes object.
Cleanup also the code: PEP 7 formatting, move variable definitions
closer to where they are used. Fix assertion checking "j" index.
* bpo-22385: Support output separators in hex methods.
Also in binascii.hexlify aka b2a_hex.
The underlying implementation behind all hex generation in CPython uses the
same pystrhex.c implementation. This adds support to bytes, bytearray,
and memoryview objects.
The binascii module functions exist rather than being slated for deprecation
because they return bytes rather than requiring an intermediate step through a
str object.
This change was inspired by MicroPython which supports sep in its binascii
implementation (and does not yet support the .hex methods).
https://bugs.python.org/issue22385
